This invention relates to a delivery fan suitable for use in, among other applications, in rotary printing presses for receiving signatures (i.e. sets of printed and folded sheets forming sections in newspaper production or book work) from a folding and cutting mechanism and depositing the signatures on a delivery conveyor or conveyor system in such a way that one signature laps over another.
In web-fed rotary printing presses, as commonly known, the webs of paper that have been printed in the printing sections are fed to the folding and cutting means whereby the webs are folded longitudinally and cut transversely into signatures of multiple pages. Disposed just downstream of the folding and cutting mechanism is a delivery fan constituting the subject of the instant invention. Typically, the delivery fan takes the form of a cylindrical rotor with a multiplicity of angled fingers or blades thereon defining pockets all equidistantly spaced one from another circumferentially of the rotor. As the rotor rotates at high speed, the signatures issuing from the folding and cutting mechanism are directed into the successive pockets and, subsequently stripped off the fingers, placed upon an underlying delivery conveyor in a neatly overlapping series.
There has been a problem, not yet totally overcome, in connection with the delivery fan of the foregoing general construction: how to prevent the signatures from rebounding and jumping out the pockets on hitting their bottoms. Japanese Unexamined Patent Publication No. 61-2650 represents one solution to that problem, suggesting lever arms that are pivotably pinned to the rotor to which the fingers are anchored providing the pockets for receiving the signatures. The lever arms extend outwardly from the rotor, one into each pocket, and are angled toward the pocket bottoms. A helical tension spring acts between the rotor and each lever arm, urging the latter against one of the fingers, so that the pockets are normally blocked by the lever arms in the neighborhood of their bottoms.
Emerging at high speed from the folding and cutting mechanism, the signatures are slid into the successive pockets of the underlying rotor as the latter rotates at a matching speed. Near the bottoms of the pockets the signatures will engage the lever arms and slide past them, causing pivotal displacement thereof against the bias of the tension springs, until they are fully received in the pockets. The spring-loaded lever arms function to brake the signatures into a soft stop against the pocket bottom, instead of allowing them to hit hard against the pocket bottom and hence fall off the pockets.
A first objection to this prior art device arises from the fact that the signatures to be handled might have several different number of pages (e.g. 4, 8, 16, or 32 pages in the case of newspaper production) and therefore of correspondingly different thicknesses. Moreover, the less the number of pages is, the more pliant are the signatures.
Suppose that the lever arms are sufficiently spring loaded to brake relatively thick signatures. Then the thinner signatures are prone to fail forcing their way fully into the pockets in opposition to the spring bias. Being so pliant, they have been easy to yield upon hitting the lever arms and so to be deformed or damaged along their edges. Or, being so light in weight, they tend to jump upwardly thereby hitting the lever arms and, upon falling down again, they get caught between the lever arms and the fingers. The result in the second instance has been irregularities in the pitch of the lapping series of signatures on the delivery conveyor.
Use of tension springs that can readily yield under the force of thin signatures would represent no fundamental remedy to this inconvenience. Such springs would be incapable of sufficiently braking thicker signatures, thereby allowing them to hit the pocket bottoms so hard as to ruin their edges, or to jump upwardly in the pockets thereby causing irregularities in the pitch of the overlapping signatures on the delivery conveyor.
Another objection concerns the mechanical construction comprising the pivotal lever arms and the helical tension springs. The pinned and spring-loaded lever arms are not so simple and inexpensive in construction as can be desired, because of the many component parts required, including the lever arms having a complex shape. Further this prior art device has been troublesome and time-consuming in assemblage, susceptible to trouble, and difficult to repair.
Japanese Unexamined Patent Publication No. 11-21002 teaches shock absorbers such as pieces of rubber or elastomeric material at the bottoms of the pockets in order to mitigate the impact of the signatures hitting the pocket bottoms. The pockets themselves are wide enough to receive the thickest signatures to be handled, so that the signatures of all different page numbers are allowed unrestricted into the pockets until they bottom against the shock absorbers and brakes.
This second prior art device is objectionable because of too much play is given in the pockets give for the thin signatures in their thickness direction. Such signatures are therefore easy to be displaced or deformed in the pockets, due in part to the centrifugal forces exerted thereon with the rotation of the delivery fan. The results has again been the disarrangement of the signatures on the delivery conveyor.
A third prior art device is cited as prior art in Japanese Unexamined Patent Publication No. 11-21002, supra, teaching a "spring steel stop" at the bottom of each pocket. Each stop is self-biased into abutment against a downstream one, with respect to the direction of fan rotation, of the fingers defining each pocket. Therefore, as in the case of the first cited prior art device, the stops may not necessarily yield to thin, pliant signatures, possibly deforming them or causing them to jump upwardly in the pockets with the consequent signature disarrangement on the delivery conveyor.
Such inconveniences will not likely occur with thicker signatures, which by virtue of their greater masses and kinetic energies will deflect the spring stops and wedge in between the stops and the fingers. This time, however, by reason of their thickness, the signatures may not smoothly disengage with the spring stops failing to align themselves neatly on the delivery conveyor.